title: Experimental quasi-single-photon transmission from satellite to earth.
abstract: Free-space quantum communication with satellites opens a promising avenue for global secure quantum network and large-scale test of quantum foundations. Recently, numerous experimental efforts have been carried out towards this ambitious goal. However, one essential step--transmitting single photons from the satellite to the ground with high signal-to-noise ratio (SNR) at realistic environments--remains experimental challenging. Here, we report a direct experimental demonstration of the satellite-ground transmission of a quasi-single-photon source. In the experiment, single photons (~0.85 photon per pulse) are generated by reflecting weak laser pulses back to earth with a cube-corner retro-reflector on the satellite CHAMP, collected by a 600-mm diameter telescope at the ground station, and finally detected by single-photon counting modules after 400-km free-space link transmission. With the help of high accuracy time synchronization, narrow receiver field-of-view and high-repetition-rate pulses (76 MHz), a SNR of better than 16:1 is obtained, which is sufficient for a secure quantum key distribution. Our experimental results represent an important step towards satellite-ground quantum communication.
authors.forename: Juan
authors.initials: J
authors.lastname: Yin
authors.forename: Yuan
authors.initials: Y
authors.lastname: Cao
authors.forename: Shu-Bin
authors.initials: SB
authors.lastname: Liu
authors.forename: Ge-Sheng
authors.initials: GS
authors.lastname: Pan
authors.forename: Jin-Hong
authors.initials: JH
authors.lastname: Wang
authors.forename: Tao
authors.initials: T
authors.lastname: Yang
authors.forename: Zhong-Ping
authors.initials: ZP
authors.lastname: Zhang
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Yang
authors.forename: Yu-Ao
authors.initials: YA
authors.lastname: Chen
authors.forename: Cheng-Zhi
authors.initials: CZ
authors.lastname: Peng
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Pan